USUALLY, IRON-RICH TOURMALINES ARE BLACK TO BLUISH-BLACK TO DEEP BROWN, WHILE MAGNESIUM-RICH VARIETIES ARE BROWN AND YELLOW, AND LITHIUM-RICH TOURMALINES ARE PRACTICALLY ANY COLOR: BLUE, GREEN, RED YELLOW, AND PINK ETC. RARELY IT IS COLOURLESS. BI-COLORED AND MUTLICOLORED CRYSTALS ARE RELATIVELY COMMON. REFLECTING VARIATIONS OF FLUID CHEMISTRY DURING CRYSTALLISATION. CRYSTALS MAY BE GREEN AT ONE END AND PINK AT EH OTHER, OUR GREEN ON THE OUTSIDE AND PINK INSIDE: THIS TYPE IS CALLED WATERMELLON TOURMALINE. SOME FORMS OF TOURMALINE ARE DICHROIC, IN THAT THEY APPEAR TO CHANGE COLOR WHEN VIEWED FROM DIFFERENT DIRECTIONS.